Sanjay Patel via llvm-dev
2016-Jul-20 20:03 UTC
[llvm-dev] Hitting assertion failure related to vectorization + instcombine
Thanks for notifying me. Yes, this was a recent change. Taking a look now. On Wed, Jul 20, 2016 at 1:49 PM, Michael Kuperstein <mkuper at google.com> wrote:> +Sanjay, who touched this last. :-) > > On Wed, Jul 20, 2016 at 12:44 PM, Ismail Badawi (ibadawi) via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > >> Hi folks, >> >> I'm hitting the below assertion failure when compiling this small piece >> of C code (repro.c, attached). >> >> My command line is: >> >> bin/clang --target=aarch64-linux-gnu -c -O2 repro.c >> >> clang is built from top of trunk as of this morning. It only happens at >> -O2, and it doesn't happen with the default target (x86_64). I tried to >> reproduce using just 'llc -O2' but didn't manage -- but I do have this >> reduced opt command line (repro.ll also attached, just generated from >> repro.c at -O0): >> >> bin/opt -instcombine -licm -simplifycfg -instcombine -loop-rotate >> -loop-vectorize -instcombine < repro.ll >> >> The failure is: >> >> opt: /scratch/1/ismail/llvm-upstream/include/llvm/ADT/APInt.h:983: bool >> llvm::APInt::operator==(const llvm::APInt&) const: Assertion `BitWidth =>> RHS.BitWidth && "Comparison requires equal bit widths"' failed. >> ...snip... >> #8 0x00000000013a8553 llvm::APInt::operator==(llvm::APInt const&) const >> /scratch/1/ismail/llvm-upstream/include/llvm/ADT/APInt.h:984:0 >> #9 0x0000000001f875b0 simplifySelectBitTest(llvm::Value*, llvm::Value*, >> llvm::Value*, llvm::APInt const*, bool) >> /scratch/1/ismail/llvm-upstream/lib/Analysis/InstructionSimplify.cpp:3388:0 >> #10 0x0000000001f87ad5 simplifySelectWithICmpCond(llvm::Value*, >> llvm::Value*, llvm::Value*, (anonymous namespace)::Query const&, unsigned >> int) >> /scratch/1/ismail/llvm-upstream/lib/Analysis/InstructionSimplify.cpp:3434:0 >> #11 0x0000000001f87f6a SimplifySelectInst(llvm::Value*, llvm::Value*, >> llvm::Value*, (anonymous namespace)::Query const&, unsigned int) >> /scratch/1/ismail/llvm-upstream/lib/Analysis/InstructionSimplify.cpp:3515:0 >> #12 0x0000000001f87fe3 llvm::SimplifySelectInst(llvm::Value*, >> llvm::Value*, llvm::Value*, llvm::DataLayout const&, >> llvm::TargetLibraryInfo const*, llvm::DominatorTree const*, >> llvm::AssumptionCache*, llvm::Instruction const*) >> /scratch/1/ismail/llvm-upstream/lib/Analysis/InstructionSimplify.cpp:3528:0 >> ...snip... >> Stack dump: >> 0. Program arguments: debugbuild/bin/opt -instcombine -licm -simplifycfg >> -instcombine -loop-rotate -loop-vectorize -instcombine >> 1. Running pass 'Function Pass Manager' on module '<stdin>'. >> 2. Running pass 'Combine redundant instructions' on function '@strsave' >> >> --- >> >> Looking at the code, the issue is with this line: >> >> if (TrueVal == X && match(FalseVal, m_And(m_Specific(X), m_APInt(C))) && >> *Y == ~*C) >> >> In this case Y is a 128-bit APInt, and so is the value that C is >> extracted from, but the m_APInt matcher has code that calls getSplatValue() >> if the matched expression has vector type. So C ends up as an 8-bit value, >> triggering the assertion failure on the call to ==. >> >> The issue is clear but I'm not sure what the correct fix should be -- >> whether this code is just not meant to work with vector types, or whether >> the call to getSplatValue() doesn't belong in the matcher, or whether there >> should be a corresponding call to getSplatValue() on the caller side, or >> something else. >> >> Any help from someone with more context would be appreciated. >> >> Thanks, >> Ismail >> >> >> _______________________________________________ >> LLVM Developers mailing list >> llvm-dev at lists.llvm.org >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >> >> >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160720/5f3d4fcd/attachment.html>
Sanjay Patel via llvm-dev
2016-Jul-20 21:59 UTC
[llvm-dev] Hitting assertion failure related to vectorization + instcombine
Quick update - the bug existed before I refactored that chunk in
InstSimplify with:
https://reviews.llvm.org/rL275911
In fact, as discussed in https://reviews.llvm.org/D22537 - because we have
a big pile of lazily copied code, the bug has an identical twin that exists
in InstCombine. I swear I didn't touch that code...yet. :)
define <2 x i32> @select_icmp_vec(<2 x i32> %x) {
%cmp = icmp slt <2 x i32> %x, zeroinitializer
%xor = xor <2 x i32> %x, <i32 2147483648, i32 2147483648>
%x.xor = select <2 x i1> %cmp, <2 x i32> %x, <2 x i32> %xor
ret <2 x i32> %x.xor
}
$ ./opt -instcombine selvec.ll -S
Assertion failed: (BitWidth == RHS.BitWidth && "Comparison requires
equal
bit widths"), function operator==, file
/Users/spatel/myllvm/llvm/include/llvm/ADT/APInt.h, line 983.
I should have a patch up for review shortly.
On Wed, Jul 20, 2016 at 2:03 PM, Sanjay Patel <spatel at rotateright.com>
wrote:
> Thanks for notifying me. Yes, this was a recent change. Taking a look now.
>
> On Wed, Jul 20, 2016 at 1:49 PM, Michael Kuperstein <mkuper at
google.com>
> wrote:
>
>> +Sanjay, who touched this last. :-)
>>
>> On Wed, Jul 20, 2016 at 12:44 PM, Ismail Badawi (ibadawi) via llvm-dev
<
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> Hi folks,
>>>
>>> I'm hitting the below assertion failure when compiling this
small piece
>>> of C code (repro.c, attached).
>>>
>>> My command line is:
>>>
>>> bin/clang --target=aarch64-linux-gnu -c -O2 repro.c
>>>
>>> clang is built from top of trunk as of this morning. It only
happens at
>>> -O2, and it doesn't happen with the default target (x86_64). I
tried to
>>> reproduce using just 'llc -O2' but didn't manage -- but
I do have this
>>> reduced opt command line (repro.ll also attached, just generated
from
>>> repro.c at -O0):
>>>
>>> bin/opt -instcombine -licm -simplifycfg -instcombine -loop-rotate
>>> -loop-vectorize -instcombine < repro.ll
>>>
>>> The failure is:
>>>
>>> opt: /scratch/1/ismail/llvm-upstream/include/llvm/ADT/APInt.h:983:
bool
>>> llvm::APInt::operator==(const llvm::APInt&) const: Assertion
`BitWidth =>>> RHS.BitWidth && "Comparison requires equal
bit widths"' failed.
>>> ...snip...
>>> #8 0x00000000013a8553 llvm::APInt::operator==(llvm::APInt
const&) const
>>> /scratch/1/ismail/llvm-upstream/include/llvm/ADT/APInt.h:984:0
>>> #9 0x0000000001f875b0 simplifySelectBitTest(llvm::Value*,
llvm::Value*,
>>> llvm::Value*, llvm::APInt const*, bool)
>>>
/scratch/1/ismail/llvm-upstream/lib/Analysis/InstructionSimplify.cpp:3388:0
>>> #10 0x0000000001f87ad5 simplifySelectWithICmpCond(llvm::Value*,
>>> llvm::Value*, llvm::Value*, (anonymous namespace)::Query
const&, unsigned
>>> int)
>>>
/scratch/1/ismail/llvm-upstream/lib/Analysis/InstructionSimplify.cpp:3434:0
>>> #11 0x0000000001f87f6a SimplifySelectInst(llvm::Value*,
llvm::Value*,
>>> llvm::Value*, (anonymous namespace)::Query const&, unsigned
int)
>>>
/scratch/1/ismail/llvm-upstream/lib/Analysis/InstructionSimplify.cpp:3515:0
>>> #12 0x0000000001f87fe3 llvm::SimplifySelectInst(llvm::Value*,
>>> llvm::Value*, llvm::Value*, llvm::DataLayout const&,
>>> llvm::TargetLibraryInfo const*, llvm::DominatorTree const*,
>>> llvm::AssumptionCache*, llvm::Instruction const*)
>>>
/scratch/1/ismail/llvm-upstream/lib/Analysis/InstructionSimplify.cpp:3528:0
>>> ...snip...
>>> Stack dump:
>>> 0. Program arguments: debugbuild/bin/opt -instcombine -licm
>>> -simplifycfg -instcombine -loop-rotate -loop-vectorize -instcombine
>>> 1. Running pass 'Function Pass Manager' on module
'<stdin>'.
>>> 2. Running pass 'Combine redundant instructions' on
function '@strsave'
>>>
>>> ---
>>>
>>> Looking at the code, the issue is with this line:
>>>
>>> if (TrueVal == X && match(FalseVal, m_And(m_Specific(X),
m_APInt(C)))
>>> &&
>>> *Y == ~*C)
>>>
>>> In this case Y is a 128-bit APInt, and so is the value that C is
>>> extracted from, but the m_APInt matcher has code that calls
getSplatValue()
>>> if the matched expression has vector type. So C ends up as an 8-bit
value,
>>> triggering the assertion failure on the call to ==.
>>>
>>> The issue is clear but I'm not sure what the correct fix should
be --
>>> whether this code is just not meant to work with vector types, or
whether
>>> the call to getSplatValue() doesn't belong in the matcher, or
whether there
>>> should be a corresponding call to getSplatValue() on the caller
side, or
>>> something else.
>>>
>>> Any help from someone with more context would be appreciated.
>>>
>>> Thanks,
>>> Ismail
>>>
>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>>
>>
>
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Hans Wennborg via llvm-dev
2016-Jul-22 13:45 UTC
[llvm-dev] Hitting assertion failure related to vectorization + instcombine
Sanjay: let me know if this is something that will apply to 3.9. Thanks, Hans On Wed, Jul 20, 2016 at 5:59 PM, Sanjay Patel via llvm-dev <llvm-dev at lists.llvm.org> wrote:> Quick update - the bug existed before I refactored that chunk in > InstSimplify with: > https://reviews.llvm.org/rL275911 > > In fact, as discussed in https://reviews.llvm.org/D22537 - because we have a > big pile of lazily copied code, the bug has an identical twin that exists in > InstCombine. I swear I didn't touch that code...yet. :) > > define <2 x i32> @select_icmp_vec(<2 x i32> %x) { > %cmp = icmp slt <2 x i32> %x, zeroinitializer > %xor = xor <2 x i32> %x, <i32 2147483648, i32 2147483648> > %x.xor = select <2 x i1> %cmp, <2 x i32> %x, <2 x i32> %xor > ret <2 x i32> %x.xor > } > > $ ./opt -instcombine selvec.ll -S > Assertion failed: (BitWidth == RHS.BitWidth && "Comparison requires equal > bit widths"), function operator==, file > /Users/spatel/myllvm/llvm/include/llvm/ADT/APInt.h, line 983. > > I should have a patch up for review shortly. > > > On Wed, Jul 20, 2016 at 2:03 PM, Sanjay Patel <spatel at rotateright.com> > wrote: >> >> Thanks for notifying me. Yes, this was a recent change. Taking a look now. >> >> On Wed, Jul 20, 2016 at 1:49 PM, Michael Kuperstein <mkuper at google.com> >> wrote: >>> >>> +Sanjay, who touched this last. :-) >>> >>> On Wed, Jul 20, 2016 at 12:44 PM, Ismail Badawi (ibadawi) via llvm-dev >>> <llvm-dev at lists.llvm.org> wrote: >>>> >>>> Hi folks, >>>> >>>> I'm hitting the below assertion failure when compiling this small piece >>>> of C code (repro.c, attached). >>>> >>>> My command line is: >>>> >>>> bin/clang --target=aarch64-linux-gnu -c -O2 repro.c >>>> >>>> clang is built from top of trunk as of this morning. It only happens at >>>> -O2, and it doesn't happen with the default target (x86_64). I tried to >>>> reproduce using just 'llc -O2' but didn't manage -- but I do have this >>>> reduced opt command line (repro.ll also attached, just generated from >>>> repro.c at -O0): >>>> >>>> bin/opt -instcombine -licm -simplifycfg -instcombine -loop-rotate >>>> -loop-vectorize -instcombine < repro.ll >>>> >>>> The failure is: >>>> >>>> opt: /scratch/1/ismail/llvm-upstream/include/llvm/ADT/APInt.h:983: bool >>>> llvm::APInt::operator==(const llvm::APInt&) const: Assertion `BitWidth =>>>> RHS.BitWidth && "Comparison requires equal bit widths"' failed. >>>> ...snip... >>>> #8 0x00000000013a8553 llvm::APInt::operator==(llvm::APInt const&) const >>>> /scratch/1/ismail/llvm-upstream/include/llvm/ADT/APInt.h:984:0 >>>> #9 0x0000000001f875b0 simplifySelectBitTest(llvm::Value*, llvm::Value*, >>>> llvm::Value*, llvm::APInt const*, bool) >>>> /scratch/1/ismail/llvm-upstream/lib/Analysis/InstructionSimplify.cpp:3388:0 >>>> #10 0x0000000001f87ad5 simplifySelectWithICmpCond(llvm::Value*, >>>> llvm::Value*, llvm::Value*, (anonymous namespace)::Query const&, unsigned >>>> int) >>>> /scratch/1/ismail/llvm-upstream/lib/Analysis/InstructionSimplify.cpp:3434:0 >>>> #11 0x0000000001f87f6a SimplifySelectInst(llvm::Value*, llvm::Value*, >>>> llvm::Value*, (anonymous namespace)::Query const&, unsigned int) >>>> /scratch/1/ismail/llvm-upstream/lib/Analysis/InstructionSimplify.cpp:3515:0 >>>> #12 0x0000000001f87fe3 llvm::SimplifySelectInst(llvm::Value*, >>>> llvm::Value*, llvm::Value*, llvm::DataLayout const&, llvm::TargetLibraryInfo >>>> const*, llvm::DominatorTree const*, llvm::AssumptionCache*, >>>> llvm::Instruction const*) >>>> /scratch/1/ismail/llvm-upstream/lib/Analysis/InstructionSimplify.cpp:3528:0 >>>> ...snip... >>>> Stack dump: >>>> 0. Program arguments: debugbuild/bin/opt -instcombine -licm >>>> -simplifycfg -instcombine -loop-rotate -loop-vectorize -instcombine >>>> 1. Running pass 'Function Pass Manager' on module '<stdin>'. >>>> 2. Running pass 'Combine redundant instructions' on function '@strsave' >>>> >>>> --- >>>> >>>> Looking at the code, the issue is with this line: >>>> >>>> if (TrueVal == X && match(FalseVal, m_And(m_Specific(X), m_APInt(C))) >>>> && >>>> *Y == ~*C) >>>> >>>> In this case Y is a 128-bit APInt, and so is the value that C is >>>> extracted from, but the m_APInt matcher has code that calls getSplatValue() >>>> if the matched expression has vector type. So C ends up as an 8-bit value, >>>> triggering the assertion failure on the call to ==. >>>> >>>> The issue is clear but I'm not sure what the correct fix should be -- >>>> whether this code is just not meant to work with vector types, or whether >>>> the call to getSplatValue() doesn't belong in the matcher, or whether there >>>> should be a corresponding call to getSplatValue() on the caller side, or >>>> something else. >>>> >>>> Any help from someone with more context would be appreciated. >>>> >>>> Thanks, >>>> Ismail >>>> >>>> >>>> _______________________________________________ >>>> LLVM Developers mailing list >>>> llvm-dev at lists.llvm.org >>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >>>> >>> >> > > > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >
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